Eccentric rotary groundwood mill

ABSTRACT

A rotary groundwood mill comprising two discs arranged to face each other and rotated in their major planes about eccentrically located axes. The discs are rotated at exactly the same speeds and in the same rotational direction. The mill structure is such that a piece of wood entrapped between the discs will be subjected to epicyclic abrasion.

United States Patent 172] lmcnim Frank P Hughes Hawkesbury, Ontario. Canada [21] Appl Nu 742,667 122] Filed .luly5, 1968 [45] Patented July 20, 1971 I73] Axsignec Canadian International Paper Company Montreal, Quebec, Canada [541 ECCENTRIC ROTARY GROUNDWOOD M11141 17 Claims, 21 Drawing Figs. [52] U.S.C1 241/146, 241/252, 241/278 {51] Int. Cl B02c 7/10 [50] Field ofSearch 241/135, 146, 206, 252, 260, 296, 278-279 56] References Cited UNITED STATES PATENTS 1,057,427 4/1913 Higbee 241/252 Primary Examiner-Donald G. Kelly Attorney-11. G. McClenahan ABSTRACT: A rotary groundwood mill comprising two discs arranged to face each other and rotated in their major planes about eccentrically located axes. The discs are rotated at exactly the same speeds and in the same rotational direction. The mill structure is such that a piece of wood entrapped between the discs will be subjected to e-picyclic abrasion.

PATENTED JULZO 19;: B, 9283 saw 1 OF 7 FIGI.

It has been suggested that a pulp having superior properties would be produced by reciprocating an abrader across a piece of. wood. A report to this effect is contained in an article entitled A Laboratory Study of a New Mechanical Pulping Process" by W. D. May and D. Atack of the Pulp and Paper Research Institute of Canada in the Pulp and Paper Magazine of Canada for Aug. 1965, pages T-422 to T-435. Another report on this subject is contained in an article by W. D. May entitled Mechanical Pulping at the Institute Part II-What Happens in Grinding, contained in pages 7 to 13 of the Winter 1966 (No. 9) issue of Trend, a publication of the Pulp and Paper Research Institute of Canada The latter article, at page II, brings out what was considered to be the unworkable nature of the process on a commercial scale. The principal object of the invention has been the provision of a novel and improved rotary groundwood mill.

More particularly, it has been an object of the invention to 1 provide such a mill which, on a commercially usable basis, can

take advantage of the benefits available from reciprocal motion of an abrader. across wood by affording relative reciprocal motion.

Another object of the invention has been the provision of a novel and improved rotary groundwood mill which provides a pulp of improved quality and which decreases the specific energy consumption required to produce the pulp.

Other and further objects, features and advantages of the invention will appear more fully from the following description ofthe invention.

SUMMARY OF THE INVENTION In accordance with the invention these objects are achieved by providing a rotary groundwood mill having an abrader disc rotatable about a first axis and having an abrader face, a magazine element disposed in juxtaposition with the abrader face of the abrader disc and being rotatable in the same rotational direction as the abrader disc about a second axis parallel to the first axis and eccentric with respect thereto, the magazine element being constructed to hold a piece of wood in contact with the abrader face and to prevent substantial movement of the piece of wood in a circumferential direction relative to the second axis, and means to rotate the abrader disc and the magazine disc about their respective axes at the same rotational speed and in the same rotational direction so that a piece of wood held by the magazine element is subjected essentially to epicyclic abrasion by relative motion between the piece of wood and the abrader face of the abrader disc resulting from the eccentricity of the axes.

BRIEF DESCRIPTION OF THE DRAWINGS ing thcinvention;

FIG. 2 is a longitudinal cross-sectional view taken generally along the line 2-2 of FIG. 1;

FIG. 3 is a reduced scale elevational view of the abrader disc ofFIG. 2 taken along the line 3-3 of FIG. 2;

FIG. 4 is a reduced scale elevational view of the magazine disc of FIG. 2 taken along the line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 2 and illustrating the abrader and magazine discs in one relative position thereof;

FIG. 5A is a cross-sectional view similar to FIG. 5 but illustuning the abrader and magazine discs rotated clockwise 90 from their FIG. 5 positions;

FIG. 5B is a cross-sectional view similar to FIG. 5 but illustrating the abrader and magazine discs rotated clockwise 180 from their FIG. 5 positions;

FIG. 5C is a cross-sectional view similar to FIG. 5 but illustrating the abrader and magazine discs rotated clockwise 270 from their FIG. 5 positions; I 7

FIGS. 6, 6A, 6B and 6C are cross-sectional views taken along the lines 6-6, (SA-6A, 68-613 and 6C-6C, respectively, ofFlGS. 5, 5A, 5B and 5C, respectively;

FIG. 7, which appears on the sameshcet as FIG. 1, is a diagrammatic illustration of typical pathsexperienced by chips or small pieces of wood relative to the face of the abrader disc of FIG. I as the abrader and magazine discs are rotated;

FIG. 8, which appears on the same sheet as FIG. 1, is a view similar to FIG. 5 but illustrating a modified construction in accordance with the invention in which the abrader disc is segmented;

FIG. 9 is a plan view, partly in cross section, of another form of rotary groundwood mill embodying the invention;

FIG. 10 is a cross-sectional view taken along the line 10-10 of FIG. 9;

FIG. II is a cross-sectional view taken along the line 11-11 of FIG. 9;

FIG. 12, which appears on the same sheet as FIG. 9, is a fragmentary sectional view taken along the line 12-12 of FIG.

FIG. 113 is a plan view, partly in cross section, of still another form of rotary groundwood mill embodying the invention;

FIG. 14 is across-sectional view, taken generally along the line 14-14 of FIG. 13; and

FIG. 15 is a longitudinal sectional view of still another form of rotary groundwood mill embodying the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Referring now to the drawings, and particularly to FIGS. 1 and 2, the groundwood mill illustrated comprises a baseplate 20 (omitted in FIG. I), a standard 21 alifixed to baseplate 20, a standard 22 mounted on baseplate 20 and a standard 23 affixed to baseplate 20. The standard 22 is slidable from left to right (FIG. 2) along plate 20 but suitable means such as guide rails (not shown) should be provided to prevent standard 22 from moving in any other direction.

The right-hand side (FIG. 2) of standard 21 is provided with a horizontal slot 24 which is T-shaped in cross section and which accommodates an enlarged head 25 and body 26 of a screw jack 27. Right end 28 of jack 27 is threaded and is engaged in a threaded hole 29 provided in standard 22. A hand wheel 30 affixed to jack 27 permits the latter to be rotated. Rotation of jack 27 causes standard 22 to slide from left to right or from right to left in FIG. 2 depending on the direction of rotation of handwheel 30. Suitable closure means (not shown) may be provided for the ends of slot 24.

The top of standard 23 is provided with a horizontal slot 31 which is T-shaped in cross section and which accommodates an enlarged head 32 and body 33 of a. screw jack 34. Upper end 35 (FIG. 2) of jack 34 is threaded and is engaged in a threaded hole 36 provided in the underside of a block 37. A handwheel 38 affixed to jack 34 permits the latter to be rotated to in turn raise and lower block 37 relative to standard 23. While only one jack 34 is shown, it will be understood that two or more such jacks may be provided to afford better support for block 37. Similarly, one or more additional jacks 27 may be provided to move standard 22. The ends of slot 31 may be closed by any suitable means, not shown. Guide rails or other suitable means (not shown) may project upwardly from standard 23 or base 20 to guide block 37 and to prevent the latter from moving except in a vertical direction.

A cylindrical sleeve 39 is mounted in a circular opening 40 in standard 22. The sleeve 39 has an enlarged annular head 41 at the inner end thereof. A shaft 42 is journaled for rotation in sleeve 39. The outer end of shaft 42 carries a sprocket wheel 43 which is affixed to shaft 42 by means of set screws 44.

An endless drive chain 45 passes about sprocket wheels 43 and 46. The sprocket wheel 46 is mounted on one end of a terior of a feed hopper 73.

47 is theoutput drive. shaft of an electricmotor 50 which may be suitably mounted on base or may be separately mounted.

A circular abrader disc 51 is affixed to the inner end of shaft 42so' as to rotate with shaft 42 and about centerline 52 thereof. The inner face 53 of abrader disc 51 is provided with a roughened surface as indicated at 54 of FIG. 3. The roughened or abrading surface of disc 51 may be any of the usual abrading surfaces commonly employed in groundwood mills, e.g., carborundum or a pattern of engraved crosslines. A radially elongated slot 55 is provided in disc 51 adjacent the radially outer edge thereof.

Suitable bearings other than sleeve 39 and flange 41 may be provided to facilitate rotation of shaft 42 and to absorb axial thrust imposed in operation.

A cylindrical sleeve 56 having an enlarged annular head 57 at the inner end thereof is mounted in a circular hole 58 in block 37. A hollow shaft 59 is journaled for rotation in sleeve 56. The inner end of shaft 59 is affixed to the outer surface of a circular magazine disc 60 so that the disc 60 will rotate about the centerline 61 of shaft 59.

. A sprocket wheel 62 is mounted adjacent the outer end of shaft 59 by means of a collar 63 and setscrews 64. Sprocket wheel 62 and a sprocket wheel 66 carry an endless drive chain 65. The sprocket wheel 66 is afi'lxed to the right-hand end of motor output shaft 47 by means of a collar 67 and setscrews 68.

The outer end of shaft 59 is carried in a ball bearing assembly 69 enclosed within an annular housing 70 provided at one end of a feed pipe 71. The feed pipe 71 is provided with a hole 72 in its upper surface which communicates with the in- A feed screw 74 is mounted in pipe 71 and extends through the center of hollow shaft 59. The inner end of feed screw 74 communicates with a central opening 75 provided in magazine disc 60. Feed screw 74 is rotated by an electric motor 76. Disc 60, shaft 59, sprocket 62 and feed screw 74 are all concentric, being arranged to rotate about axis 61. The feed pipe 71 and hopper 73 are supported from block 37 by a projecting bracket arm 77.

The sprocket and chain drive 43-45-46 and the sprocket and chain drive 62-65-66 are arranged to rotate the shafts 39 and 59 at identical speeds so that the abrader disc 51 and the magazine disc 60 will rotate at identical speeds. However, the rotation of disc 60 will be eccentric relative to disc 51 because the axes of rotation 61 and 52 are vertically displaced relative to each other by an amount determined by the setting of jack screw 34. The eccentricity is preferably of the same order of magnitude as a typical wood chip, e.g., between about onefourth inch and 1 inch.

The inner face of magazine disc 60 is an inclined annular surface 78 and may, if desired, be made concave. The incline is radially outward and toward the inner face 53 of disc 51 so that a maximum spacing occurs between the discs at the opening 75 and a minimum spacing occurs between the discs around the periphery of .disc 60. The inner face of disc 60 is thus dished. As shown in FIGS. 1 and 2, the circular space 79 between the opposing faces of the discs is, in cross section, essentially a trapezoid with vertical bases.

The inner face 78 of disc 60 is provided with a threaded hole adjacent the outer periphery thereof. The threaded hole accommodates the threaded end 80 of a pin 81. The pin 81 is aligned with and enters slot 55. There is preferably a sliding fit between pin 81 and slot 55. The pin 81 acting in slot 55 impels the magazine disc 60 and the abrader disc 51 to rotate at precisely the same speeds.

In operation, wood chips loaded into hopper 73 fall into feed pipe 71 and are advanced by screw conveyor 74 through the hollow shaft 59 into space 79 between discs 51 and 60. Chips entering space 79 are urged toward the periphery of disc 60 by the combined action of gravity, centrifugal force and pressure exerted by following chips.

As is best shown in FIG. 4, the inner face 78 of disc 60 is provided with a series of radially extending ribs 82. The ribs 82 serve to prevent chips from moving circumferentially along surface 78. Instead, the chips are trapped between ribs and can move only in a radial direction.

Until the chips are worn down by abrasion resulting from contact with face 53 of disc 51, the chips cannot progress far in a radial direction. However, as they become smaller they can move radially outward toward the periphery of disc 60.

The position of the axis 61 of disc 60 may be varied in the vertical direction by means of the screwjack 34. If the screwjack 34 is adjusted to set disc 60 in exact concentricity with disc 51, then the chips between then will experience no abrasion, for the two discs 51 and 60 will rotate as a unit, both ofthe discs rotating in the same direction.

But if the screwjack 34 be lowered, say one-half inch, there will be relative motion between the two discs, and the chips will be abraded. The path of a chip referred to the abrader disc 51 will be an oval, or slightly irregular ellipse of dimensions depending upon the eccentricity set by jackscrew 34 and upon the position of the ellipse on disc 51. This path may be followed through FIGS. 5, 6 and 7. The ratio of the eccentricity of the axis to the diameter of the discs is exaggerated for clarity in these figures. A typical value of the eccentricity might be one-half inch.

Referring to FIG. 5, a wood chip C is shown located at the same radial location from the center of rotation 52 of magazine disc 51 as the pin 81. In the position shown in FIG. 5, the chip C will be at a radius from the center of disc 51 represented by vector 83. Now consider the discs rotated through 90 to the position shown in SA. Here the chip C is unmoved with respect to the pin 81 in disc 60, but has moved one-half of an inch across the abrader disc 51 and is now at a distance from the center of rotation 52 of disc 51 represented by vector 84, which equals vector 83-one-half inch in length. These vectors are drawn on FIG. 7 for comparison. Let the discs be rotated a further 90 to the position shown in FIG. 53. Now the pin 81 has travelled down the slot 55 the full I inch, twice the eccentricity as set by jackscrcw 34, and the chip C, still in the same position as before with respect to disc 60, has moved 1 inch toward the periphery of disc 51, or the vector 85 equals vector 83] inch in length.

FIG. 5C represents the situation after 270 rotation where the chip C has moved back from the periphery of disc 51 by one-half inch, yielding a vector 86 equal to vector 83onehalf half inch in length. Finally, 360 of rotation brings chip C back to its starting point on disc 51, as shown in FIG. 5.

The chip has now described an elongated ellipse on the abrader disc 51 and on further rotation will repeat the same path over disc 51 exactly, which is the optimum condition for the separation of fibers.

' Amplifying this explanation, if an observer could be located on disc 51, rotate with it and note the path traced by the chip C, he would observe it as the elongated ellipse shown as 87 in FIG. 7. Other chips in other positions about disc 60 would trace typical paths as 88, 89 and 90, as shown in FIG. 7.

A different viewpoint is shown in FIGS. 6-6C. Referring to FIG. 6B, the pin 81 is at the bottom of its stroke in slot 55. Consider a chip C1 held by disc 60 in such a position that it just touches the slot 55 in disc 51. Rotation of the discs through 90 moves the chip C1 away from the slot 55 (FIG. 6C) by an amount equal to the eccentricity. A further90 rotation moves the chip C1 to a distance of twice the eccentricity from the edge of the slot, as shown in FIG. 6. After 270 of rotation (FIG. 6A) the chip Cl moves back toward the slot by an amount equal to the eccentricity and after a full rotation the chip (FIG. 6B) again touches the edge of the slot.

As the chips abrade, the fibers removed from them form balls. After a time each ball will free itself from the continually depleted parent chip and will travel toward the periphery of the discs and slip between them through the space 91 at their edges. The space 91 (between discs 51 and 60) is adjustable by jackscrew 27. The fiber balls are flung outward by centrifugal force, are caught by a housing or slinger 92 and fall on a conveyor 93 to be carried to the next stage of the process. This next stage is usually referred to as clearing and involves dispersing the fiber bundles into single fibers, as in well known in the art.

The slinger 92 is preferably formed by two overlapping housing elements 94 and 95 suitably affixed to standard 22 and block 37, respectively, as by screws 96 and 97, respectively, acting in flange projections of the housing elements. The slinger 92 surrounds the discs 51 and 60 except for the bottom portion thereof which is open for fibers to fall onto conveyor 93.

A better grade of pulp may be made by forming the abrader disc 51 into four radial sectors or sections as shown in FIG. 8 at 51A, 51B, 51C and 51D. These quadrants 51A-51D are mounted concentrically about centerline 52 and are counterbalanced. The magazine disc 60 in this case carries four pins, 81A81D, which fit into respective slots 55A55D and synchronize the respective quadrants 51A-51D. This formation insures that the paths of the chips all approximate 87 and 88 (FIG 7).

Referring now to the embodiment of the invention illustrated in FIGS. 9-12, there is shown a construction in which logs rather than chips may be subjected to the epicyclic abra sion action.

A frame element 100 is provided with a circular plate 101 and downwardly and outwardly extending support legs 102, 103 and 104 which may be affixed to the floor or a bascplate indicated diagrammatically by the dashed line 105. A cylindrical body 106 projects upwardly from the center of plate 101. The body 106 is preferably an integral part of the frame element 100.

An annular bearing element 107 is mounted on plate 101 and surrounds the lower portion of body 106. Bearing element 107 supports the lower end of an annular flange 108 which projects downwardly from an abrader disc 109. The disc 109 has an upper abrading surface 110 which corresponds to the surface 53 of disc 51. The center of disc 109 is bored so that the disc can be mounted on and be rotated relative to body 106. Body 106 will be provided with a suitable bearing surface for this purpose. The centerline about which disc 109 rotates is shown at 111.

The outer surface of annular flange 108 carries a toothed sprocket wheel 112. An endless drive chain 1w passes around wheel 112 and connects the latter to a drive sprocket wheel 114 carried on a shaft 115. Shaft 115 also carries a spur gear 116 which meshes with a worm gear 117 mounted on a shaft 118. The shaft 118 is driven by an electric motor 119 through a reduction gear box 120. The motor 119 thus serves to rotate abrasion disc 109 about centerline 111.

As is best shown in FIGS. and 12, cylindrical block 106 is eccentrically bored to accommodate a shaft 121 which rotates about a centerline 122 which is eccentric with respect to centerline 111.

Shaft 121 is affixed at its upper end to an inclined striker plate 123 which in turn is affixed to the under surface 124 of a magazine disc 125. Rotation of shaft 121 about centerline 122 will thus produce corresponding rotation of disc 125 about centerline 122.

Shaft 121 extends downward below the bottom of plate 101 and has affixed thereto a sprocket wheel 126. An endless drive chain 127 passes around sprocket wheel 126. Chain 127 also passes around a sprocket wheel 128 mounted on shaft 115. The sprocket wheels are arranged so that motor 119 will cause discs 109 and 125 to rotate at the same r.p.m.

As is best shown in FIGS. 10 and 11, under surface 124 of magazine disc 125 is shaped in the form of a one turn screw. Hence the magazine space 129 between surface 110 and 124 will have a height varying in accordance with the one turn screw shape of surface 124.

A guard plate 130projects upwardly from magazine disc 125. The plate 130 has parallel sidepieces 131 and 132 joined by. a semicircular piece 133 forming an open channel to receive logs. The radially inner end of guard plate is approximately aligned with centerline 1111 of abrader disc 109.

Logs from a suitable source (not shown) are dropped vertically essentially in alignment with axis 122 ofdisc 125. A log L in such a position is illustrated in dashed lines in FIG. 10. As the lower edge of the log L hits striker plate 123, the log falls sideways, as indicated by arrow 134, into the open channel formed by guard plate 130. The guard plate 130 is located so that logs falling into the magazine space 129 will be at the low point of the pitch of the one turn screw surface 124. A log in this position is shown at L1 in FIG. 10. As the log L1 abrades from action of abrasion disc 109, the: log will be carried along into the magazine space. Four successive positions of log L1 in the magazine space are shown at 135, 136, 137 and 138 in FIG. 11. As a log moves on into the magazine it leaves room for a succeeding log to enter the magazine. The direction of rotation of the discs must be such as to drive the logs into the turn ofthe screw.

The fiber abraded from the logs by contact with abrader disc 109 escapes from bctwecnthc discs 109 and 125 and is directed by a slinger or housing 139 onto a discharge conveyor belt 140.

Since logs generally present a much larger surface than a single chip, a greater degree of eccentricity can be accommodated. Thus in handling chips, as in FIG. 1, a typical eccentricity will be of the order of one-half inch. A typical eccentricity for the arrangement of FIG. 10 would be 2 inches. Moreover, in handling logs, as distinguished from chips, a larger error in the precision of equality of rotation can be tolerated. i

In the arrangement of FIGS. 9 --12 each log will be held by the magazine walls so as to be subject essentially only to straight line motion between the log and the abrader surface. However, better control of the log in this respect is afforded by the modified construction illustrated in FIGS. 13 and 14.

Referring now to FIGS. 13 and 14, a frame element is provided with a circular plate 151 and downwardly and outwardly extending support legs 152, 15 3 and 154 which may be affixed to the floor or to a bascplate indicated diagrammatically by line 155. A cylindrical body 156 projects upwardly from the center of plate 151. The body 156 is integral with plate 151.

An annular bearing element 157 is mounted on plate 151 and surrounds the lower portion of body 156. The bearing 157 supports the lower end of an annular flange 158 which projects downwardly from an abrader disc 159. The disc 159 has an inclined upper abrading surface 160 which corresponds to the surface 110 of disc 109. The center of disc 159 is bored so that the disc 159 can be mounted on and be rotated relative to body 156. Body 156 will be provided. with a suitable bearing surface for this purpose. The centerline about which disc 159 rotates is shown at 161.

The outer surface of annular flange 158 carries a toothed sprocket wheel 162. An endless'drive chain 163 passes around wheel 162 and also a sprocket wheel 164 carried on a shaft 165 of a motor 166.

Cylindrical block 156 is provided with an eccentrically located annular projection 167. The projection 167, block 156 and plate 151 are eccentrically bored to accommodate a vertical shaft 168. The lowerend of shaft 168 carries a sprocket wheel 169 about which passes an endless drive chain 170. The chain 170 also passes around a sprocket wheel 171 on shaft 165. The arrangement is such that motor 166 drives disc 159 and shaft 168 at identical rpm. The centerline of shaft 168 is indicated at 172 and the distance between centerlines 161 and 172 establishes the abrader-magazine eccentricity.

At its upper end shaft 168 carries a collar 173 having four yokes 174, 175, 176 and 177 spaced apart 90. Each of the yokes l74177 is connected by a universal joint to a respective one of arms 178, 179, and 181. The other ends of arms 178-481 are similarly connected by universal joints to yokes provided in the upper surfaces of respective ones of channel shaped clamp elements 183, 184, 185 and 186. The

arms 178-181 are each urged to swing downwardly by a i respective one of bowed spring elements 187, I88, 189 and become worn away by the abrasion, the arms 178-181 will be urged to swing downwardly to hold the logs against the abrasion surface 160.

In order to control the relative motion between the logs and the abrader disc 159, a set of ways 191 and bearing elements 192 are provided to constrain each clamp. The ways 191 are rigidly affixed to the abrader disc 159 which produces a rectilinear motion of each log with respect to the abrader disc due to the eccentricity of the abrader disc relative to shaft 168. It will be evident that disc 159 need not be complete since an abrasion surface is only required where the logs contact the abrader disc.

Abraded fibers escape over the edge of disc 159 and are carried by a slinger or housing 193 onto a conveyor belt 194. To avoid fibers missing the belt, the slinger 193 may be spaced very close to the periphery of disc 159 or a chute may be provided to carry fibers onto the belt.

To increase the throughput of the grinder illustrated in FIGS. 13 and 14, additional arms and channels may be provided to hold additional logs in contact with the abrader disc.

' To increase the throughput of a chip grinder of the type illustrated in FIGS. 1-4, additional discs may be mounted on common shafts, as illustrated in FIG. 15.

Referring now to FIG. 15, there is shown a frame 200 comprising a base 201 and spaced, parallel, upright standards 202 and 203. The standards 202 and 203 are provided with aligned circular holes 204 and 205, respectively, which afford bearing surfaces for a hollow shaft 206.

A drive gear 207 is carried onthe right end of shaft 206 and is arranged to be rotated through a suitable power train (not shown). The left end of hollow shaft 206 communicates with a wood chip hopper 208. A feed screw 209 located within shaft 206 and driven by a motor 210 advances wood chips to the right along the center of shaft 206.

The standards 202 and 203 are provided with inwardly extending annular flanges 211 and 212, respectively, around holes 204 and 205, respectively. The horizontal annular hearing surfaces 213 and 214 of flanges 211 and 212, respectively, are concentric about a centerline 215 which is eccentric with respect to centerline 216 of shaft 206.

The magazine disc of FIG. is indicated generally by the reference numeral 217 and comprises three separate annular segments 218, 219 and 220.

The segments 218 and 220 each have a projecting annular flange 221 and 222, respectively, which rides on a respective one of annular bearing surfaces 213 and 214 to support magazine disc 217. Segments 218-220 are held rigidly in the parallel, spaced-apart positions shown in FIG. 15 by a series of circumferentially spaced threaded bolts 221' acting in bored flange projections 222' extending from the periphery of the segments. The assembly is locked together in the position shown by nuts 223.

A pair of abrader discs 224 and 225 having abrasion surfaces on both sides thereof are mountedon shaft 206 for rotation with shaft 206. Abrader disc 224 is located midway between magazine disc segments 218 and 219 while disc 225 is located midway between magazine disc segments 2l9and 220.

Magazine disc segment 218 has an inclined annular face 226 which corresponds to the face 78 of magazine disc 60 of FIG. 2. Magazine disc segment 220 has a similar but oppositely inclined face'227. Magazine disc' segment 219 is provided with oppositely inclined annular faces 228 and 229 opposing abrader discs 224 and 225, respectively. The annular space between face 226 and disc 224 is designated 230; the annular space between face 228 and disc 224 is designated 231; the annular space between face 229 and disc 225 is designated 232; and the annular space between face 227 and disc 225 is designated 233. The spaces 230-233 each corresponds to the space 79 of FIG. 2. Each of the faces 226-229 is ribbed to hold chips as described in connection with the ribs 82 of FIG. 4.

Hollow shaft 206 is provided with spaced apertures 235, 236 and 237 communicating with the spaces 230, 231-232, and 233, respectively, so that chips advanced by feed screw 209 will enter the spaces230-233.

A drive gear 238 which may be mounted on or be integral with magazine disc segment 220 is arranged to be rotated through a suitablepowcr train (not shown) which will drive magazine 217 at the same r.p.m. as shaft 206.

To insure exact equality of r.p.m., a pin 239 is rigidly carried by segments 218, 219 and 220. The pin 239 passes through elongated slots 240 and 241 provided in abrader discs 224 and 225, respectively, and which correspond in shape and function to the slot 55 of FIG. 2. If more than one of the pins 239 are provided they will be spaced circumferentially, preferably an equal angular distance apart and the abrader discs must be split into as, many sectors as there are pins.

Fibers thrown out from between an abrasion disc and the corresponding magazine disc segment face are carried by a slinger 242 onto a discharge conveyor belt 243.

The term concave" as used herein to describe the face of the magazine disc which faces the abrader face of the abrader disc is intended to include both a curved concave surface and a polygonal surface having an exterior angle greater than For example, considering the magazine disc 60 of FIG. 2 to be a polygon, the exterior angle formed by the junction of the inclined portions of the surface 78 is greater than 180. The term "epicyclic" as used herein is intended to refer to the relative motions involved resulting from eccentricity of the axes of rotation. Thus the term has reference to the conventional meaning of the motion of a small circle the center ofwhich moves around within the circumference of a larger circle.

While'the invention has been described in connection with specific embodiments thereof and in a specific use, various modifications thereof will occur to those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.

What I claim is:

1. A rotary groundwood mill, comprising:

a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis;

b. a magazine element disposed in juxtaposition with said abrader face of said abrader disc to provide a magazine space therebetween and being rotatable about a second axis parallel to said first axis and eccentric with respect thereto, said magazine element being constructed to hold a piece of wood in contact with said abrader face without substantial circumferential motion of said piece of wood relative to said second axis; and

c. means to rotate said abrader disc and said magazine element, said means comprising a mechanical intercoupling of said abrader disc and said magazine element to compel rotation of said abrader disc and said magazine element at substantially the same rotational speeds so that said piece of wood held by said magazine element is subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes.

2. A rotary groundwood mill, comprising:

a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis; I

b. a magazine disc disposed in juxtaposition with said abrader face of said abrader disc to provide a magazine abrader disc and said magazine disc to compel rotation of said abrader disc and said magazine disc at substantially the same rotational speeds so that said wood chips held by said magazine disc are subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes.

3. A rotary groundwood mill as set forth in claim 2 in which said magazine disc has a generally concave face facing said abrader face, said generally concave face having radial ribs for preventing substantial circumferential motion of said wood chips relative to said second axis.

4. A rotary groundwood mill as set forth in claim 2 in which said means to rotate said magazine disc comprises a hollow shaft communicating at one end thereof with said magazine space and in which means are provided to force wood chips through said hollow shaft and into said magazine space.

5. A rotary groundwood mill comprising:

a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis;

b. a magazine disc disposed in juxtaposition with said abrader face of said abrader disc to provide amagazine space therebetween and being rotatable about a second axis'parallel to said first axis and eccentric with respect thereto, said magazine disc being constructed to hold wood chips in contact with said abrader face without substantial circumferential motion of said wood chips relative to said second axis; and

c, means to rotate said abrader disc and said magazine disc at substantially the same rotational speeds so that said wood chips held by said magazine disc are subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes,

said means comprising a radially elongated slot in one of said discs radially spaced from the axis of rotation thereof and an axially extending pin projecting from the other of said discs in alignment with said slot, said pin extending into said slot to compel rotation of said discs at identical rotation speeds.

6 A rotary groundwood mill as set forth in claim 2, comprising means to adjust the eccentricity of said axes.

7. A rotary groundwood mill as set forth in claim 2 compris' ing means to move one of said discs in an axial direction relative to the other of said discs to thereby adjust the circum ferential gap between said discs.

8. A rotary groundwood mill as set forth in claim 2 in which said abrader disc comprises a plurality of radial sectors and in which separate means is provided intercoupling each of said radial sectors and said magazine disc to prevent each of said radial sectors from rotating at a speed different from the speed of said magazine disc.

9. A rotary groundwood mill, comprising:

a. a first shaft rotatable about a first axis;

b. an abrader disc mounted on said first shaft for rotation therewith about said first axis; said abrader disc having an abrader face disposed transversely of said first axis, said abrader disc having a radially elongated slot in said abrader face at a radial position adjacent the periphery of said abrader disc;

c. a second shaft rotatable about a second axis parallel to said first axis and eccentric with respect thereto, said second shaft being hollow;

d. a magazine disc mounted on said second shaft for rota tion therewith, said magazine disc having an annular face disposed in juxtaposition with said abrader face and having a central opening communicating with the hollow interior of said second shaft, said annular face being concave to define, with said abrader face, a magazine space between said discs;

e. means comprising a series of radially extending ribs on said annular face of said magazine disc to hold wood chips in said magazine space in contact with said abrader face without substantial circumferential motion of said chips relative to said second axis;

f. a pin carried on said magazine disc and projecting axially from said annular face in alignment with said slot, said pin extending into said slot to compel said discs to rotate at identical speeds; I

g. means to supply wood chips to the interior of said hollow second shaft;

h. feed means arranged to force said wood chips to move through the interior of said hollow second shaft and into said magazine space; and

. means to rotate said first and second shafts at substantially the same rotational speeds so that said wood chips in said magazine space are subjected to substantially epicyclic abrasion by relative motion between said wood chips and said abrader face resulting from said eccentricity of said axes.

10. A rotary groundwood mill, comprising:

a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis;

b. a magazine disc disposed in juxtaposition with said abrader face of said abrader disc to provide a magazine space therebetween and being rotatable about a second axis parallel to said first axis and! eccentric with respect thereto, the face of said magazine disc disposed toward said abrader face being shaped as a one turn screw to hold a log or like piece of wood in contact with said abrader face without substantial circumferential motion of said piece of'wood relative to said second axis; and

c. means comprising a mechanical intercoupling of said abrader disc and said magazine disc to rotate said abrader disc and said magazine disc at substantially the same rotational speeds so that said piece of wood held by said magazine element is subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes.

111. A rotary groundwood mill as set forth in claim 1 in which said magazine element comprises a clamp member constructed to hold a log or like piece of wood in contact with said abrader face without substantial circumferential motion of said piece of wood relative to said second axis and in which means is provided positively to urge said clamp member toward said abrader face.

12. A rotary groundwood mill as set forth in claim 1 in which said magazine element comprises a plurality of concentrically mounted clamp members disposed at spaced circumferential positions about said second axis and each constructed to hold a log or like piece of wood in contact with said abrader face without substantial circumferential motion of said pieces of wood relative to said second axis.

13. A rotary groundwood mill as set forth in claim 12 in which spring means are provided for each of said clamp members to urge the latter positively toward said abrader face.

14. A rotary groundwood mill, comprising:

a. a shaft rotatable about a first axis;

b. a plurality of axially spaced abrader discs mounted on said shaft for rotation therewith and each having an abrader face on each side thereof;

c. a plurality of axially spaced annular magazine discs each having a concave face disposed in juxtaposition with a respective one of said abrader faces to define an individual magazine space between each pair of juxtaposed abrader and concave faces;

' g. means to rotate said shaft and said unit of magazine discs atthe same rotational speed about said first and second axes, respectively, so that wood chips in each of said magazine spaces are subjected to substantially epicyclic abrasion by relative motion between said wood chips and the corresponding one of said abrader faces resulting from said eccentricity of said axes.

IS. A rotary groundwood mill as set forth in claim 14 in which each of said abrader discs has a radially elongated slot,

said slots being axially aligned, and in which pin means extending through said slots and rigidly held in said magazine discs prevents said magazine discs and said abrader discs from rotating at different speeds.

16. A rotary groundwood mill as set forth in claim 15 in which said shaft is hollow and in which said wood chips supply means includes the hollow space in said shaft, said shaft having a plurality of openings providing wood chip passages between the interior of said shaft and said magazine spaces.

17. A rotary groundwood mill as set forth in claim 1 in which said abrader face of said abrader disc is substantially flat. 

1. A rotary groundwood mill, comprising: a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis; b. a magazine element disposed in juxtaposition with said abrader face of said abrader disc to provide a magazine space therebetween and being rotatable about a second axis parallel to said first axis and eccentric with respect thereto, said magazine element being constructed to hold a piece of wood in contact with said abrader face without substantial circumferential motion of said piece of wood relative to said second axis; and c. means to rotate said abrader disc and said magazine element, said means comprising a mechanical intercoupling of said abrader disc and said magazine element to compel rotation of said abrader disc and said magazine element at substantially the same rotational speeds so that said piece of wood held by said magazine element is subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes.
 2. A rotary groundwood mill, comprising: a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis; b. a magazine disc disposed in juxtaposition with said abrader face of said abrader disc to provide a magazine space therebetween and being rotatable about a second axis parallel to said first axis and eccentric with respect thereto, said magazine disc being constructed to hold wood chips in contact with said abrader face without substantial circumferential motion of said wood chips relative to said second axis; and c. means to rotate said abrader disc and said magazine disc said means comprising a mechanical intercoupling of said abrader disc and said magazine disc to compel rotation of said abrader disc and said magazine disc at substantially the same rotational speeds so that said wood chips held by said magazine disc are subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes.
 3. A rotary groundwood mill as set forth in claim 2 in which said magazine disc has a generally concave face facing said abrader face, said generally concave face having radial ribs for preventing substantial circumferential motion of said wood chips relative to said second axis.
 4. A rotary groundwood mill as set forth in claim 2 in which said means to rotate said magazine disc comprises a hollow shaft communicating at one end thereof with said magazine space and in which means are provided to force wood chips through said hollow shaft and into said magazine space.
 5. A rotary groundwood mill comprising: a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis; b. a magazine disc disposed in juxtaposition with said abrader face of said abrader disc to provide a magazine space therebetween and being rotatable about a second axis parallel to said first axis and eccentric with respect thereto, said magazine disc being constructed to hold wood chips in contact with said abrader face without Substantial circumferential motion of said wood chips relative to said second axis; and c. means to rotate said abrader disc and said magazine disc at substantially the same rotational speeds so that said wood chips held by said magazine disc are subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes, said means comprising a radially elongated slot in one of said discs radially spaced from the axis of rotation thereof and an axially extending pin projecting from the other of said discs in alignment with said slot, said pin extending into said slot to compel rotation of said discs at identical rotation speeds.
 6. A rotary groundwood mill as set forth in claim 2, comprising means to adjust the eccentricity of said axes.
 7. A rotary groundwood mill as set forth in claim 2 comprising means to move one of said discs in an axial direction relative to the other of said discs to thereby adjust the circumferential gap between said discs.
 8. A rotary groundwood mill as set forth in claim 2 in which said abrader disc comprises a plurality of radial sectors and in which separate means is provided intercoupling each of said radial sectors and said magazine disc to prevent each of said radial sectors from rotating at a speed different from the speed of said magazine disc.
 9. A rotary groundwood mill, comprising: a. a first shaft rotatable about a first axis; b. an abrader disc mounted on said first shaft for rotation therewith about said first axis; said abrader disc having an abrader face disposed transversely of said first axis, said abrader disc having a radially elongated slot in said abrader face at a radial position adjacent the periphery of said abrader disc; c. a second shaft rotatable about a second axis parallel to said first axis and eccentric with respect thereto, said second shaft being hollow; d. a magazine disc mounted on said second shaft for rotation therewith, said magazine disc having an annular face disposed in juxtaposition with said abrader face and having a central opening communicating with the hollow interior of said second shaft, said annular face being concave to define, with said abrader face, a magazine space between said discs; e. means comprising a series of radially extending ribs on said annular face of said magazine disc to hold wood chips in said magazine space in contact with said abrader face without substantial circumferential motion of said chips relative to said second axis; f. a pin carried on said magazine disc and projecting axially from said annular face in alignment with said slot, said pin extending into said slot to compel said discs to rotate at identical speeds; g. means to supply wood chips to the interior of said hollow second shaft; h. feed means arranged to force said wood chips to move through the interior of said hollow second shaft and into said magazine space; and i. means to rotate said first and second shafts at substantially the same rotational speeds so that said wood chips in said magazine space are subjected to substantially epicyclic abrasion by relative motion between said wood chips and said abrader face resulting from said eccentricity of said axes.
 10. A rotary groundwood mill, comprising: a. an abrader disc rotatable about a first axis and having an abrader face disposed transversely of said first axis; b. a magazine disc disposed in juxtaposition with said abrader face of said abrader disc to provide a magazine space therebetween and being rotatable about a second axis parallel to said first axis and eccentric with respect thereto, the face of said magazine disc disposed toward said abrader face being shaped as a one turn screw to hold a log or like piece of wood in contact with said abrader face without substantial circumferential motion of said piece of wood relative to said second axis; and c. means comprisiNg a mechanical intercoupling of said abrader disc and said magazine disc to rotate said abrader disc and said magazine disc at substantially the same rotational speeds so that said piece of wood held by said magazine element is subjected to substantially epicyclic abrasion by relative motion between said piece of wood and said abrader face of said abrader disc resulting from said eccentricity of said axes.
 11. A rotary groundwood mill as set forth in claim 1 in which said magazine element comprises a clamp member constructed to hold a log or like piece of wood in contact with said abrader face without substantial circumferential motion of said piece of wood relative to said second axis and in which means is provided positively to urge said clamp member toward said abrader face.
 12. A rotary groundwood mill as set forth in claim 1 in which said magazine element comprises a plurality of concentrically mounted clamp members disposed at spaced circumferential positions about said second axis and each constructed to hold a log or like piece of wood in contact with said abrader face without substantial circumferential motion of said pieces of wood relative to said second axis.
 13. A rotary groundwood mill as set forth in claim 12 in which spring means are provided for each of said clamp members to urge the latter positively toward said abrader face.
 14. A rotary groundwood mill, comprising: a. a shaft rotatable about a first axis; b. a plurality of axially spaced abrader discs mounted on said shaft for rotation therewith and each having an abrader face on each side thereof; c. a plurality of axially spaced annular magazine discs each having a concave face disposed in juxtaposition with a respective one of said abrader faces to define an individual magazine space between each pair of juxtaposed abrader and concave faces; d. means to retain said magazine discs as a unit and to support said unit for rotation about a second axis parallel to said first axis and eccentric with respect thereto; e. means to supply wood chips to each of said magazine spaces; f. means comprising radial ribs on each of said concave faces to hold wood chips in contact with the corresponding abrader face without substantial circumferential motion relative to said second axis; g. means to rotate said shaft and said unit of magazine discs at the same rotational speed about said first and second axes, respectively, so that wood chips in each of said magazine spaces are subjected to substantially epicyclic abrasion by relative motion between said wood chips and the corresponding one of said abrader faces resulting from said eccentricity of said axes.
 15. A rotary groundwood mill as set forth in claim 14 in which each of said abrader discs has a radially elongated slot, said slots being axially aligned, and in which pin means extending through said slots and rigidly held in said magazine discs prevents said magazine discs and said abrader discs from rotating at different speeds.
 16. A rotary groundwood mill as set forth in claim 15 in which said shaft is hollow and in which said wood chips supply means includes the hollow space in said shaft, said shaft having a plurality of openings providing wood chip passages between the interior of said shaft and said magazine spaces.
 17. A rotary groundwood mill as set forth in claim 1 in which said abrader face of said abrader disc is substantially flat. 